LFCS Essential Commands Practice Test 4 — 15 Questions

Question 1

A DevOps engineer wants to measure how long a specific command takes to execute. Which command should be used?

Accepted Answer

time. The `time` command is specifically designed to measure the execution duration of a command, reporting real time, user CPU time, and system CPU time. It wraps the target command and tracks the elapsed wall-clock time and resource usage, making it the precise tool for benchmarking command performance.

Answer

date

Answer

uptime

Answer

wall

Question 2

An administrator runs 'ls -la' and sees the following entry for a file: 'lrwxrwxrwx 1 root root 24 Jan 10 12:00 link -> /etc/passwd'. If the target file /etc/passwd is deleted, what happens to the link file?

Accepted Answer

The link becomes a broken symbolic link. The entry 'lrwxrwxrwx' indicates a symbolic link (symlink), which stores a path to the target file rather than sharing its inode. When the target /etc/passwd is deleted, the symlink still exists but points to a non-existent path, making it a broken (dangling) symlink. Accessing it will result in a 'No such file or directory' error.

Answer

The link becomes a hard link to the deleted file's inode

Answer

The link becomes a regular file with the same content

Answer

The link is automatically deleted

Question 3

To compress a file while preserving the original file, which command should be used?

Accepted Answer

gzip -k file.txt. The `-k` (or `--keep`) flag in `gzip` instructs the utility to compress the file while retaining the original uncompressed file. By default, `gzip` replaces the original file with a compressed version (appending `.gz`), so `-k` is the explicit option to preserve the source file.

Answer

gzip file.txt

Answer

gzip -d file.txt.gz

Answer

gzip -1 file.txt

Question 4

A system administrator wants to display a list of all currently running processes with their parent process IDs. Which command is most appropriate?

Accepted Answer

ps -ef. (ps -ef) is correct because the 'ps' command with the '-e' flag displays all processes, and the '-f' flag provides a full-format listing that includes the PPID (parent process ID) in the output. This directly meets the requirement to list all currently running processes with their parent process IDs.

Answer

pstree

Answer

jobs

Answer

top

Question 5

An administrator runs 'df -h' and notices that /dev/sda1 is 95% full. The administrator needs to identify the largest files in the filesystem. Which command sequence is most efficient?

Accepted Answer

du -sh /* | sort -rh. It efficiently identifies the largest directories and files at the top level of the filesystem using `du -sh /*` to summarize disk usage per top-level item, then pipes to `sort -rh` to sort by human-readable sizes in descending order. This avoids scanning every single file recursively, making it the fastest approach for a full filesystem.

Answer

find / -type f -size +100M

Answer

ls -lR / | sort -k5 -rn

Answer

find / -type f -exec du -sh {} \;

Question 6

To display the first 10 lines of a file named 'log.txt', which command is correct?

Accepted Answer

head log.txt. The `head` command is designed to display the first 10 lines of a file by default. Running `head log.txt` outputs the first 10 lines of the file without any additional options, making it the correct choice for this task.

Answer

less log.txt

Answer

tail log.txt

Answer

cat log.txt

Question 7

A user is unable to write to a file. The output of 'ls -l file' shows '-r--r--r--'. Which command will grant write permission to the owner?

Accepted Answer

chmod u+w file. The file's permissions are '-r--r--r--', meaning the owner has only read permission. The 'chmod u+w file' command adds write permission for the owner (u) because 'u' refers to the user/owner. This directly addresses the owner's lack of write access.

Answer

chmod o+w file

Answer

chmod a+w file

Answer

chmod g+w file

Question 8

An administrator needs to find the process ID of the cron daemon. Which combination of commands is most effective?

Accepted Answer

pidof cron. `pidof cron` directly returns the numeric process ID(s) of the cron daemon by searching the process name in the `/proc` filesystem. It is the most straightforward command for this specific task, as it outputs only the PID without additional formatting or filtering.

Answer

top -p $(pgrep cron)

Answer

pgrep cron

Answer

ps -C cron -o pid=

Question 9

A system administrator needs to change the group ownership of a file to 'developers' and set the setgid bit on a directory. Which two commands accomplish these tasks? (Choose two.)

Accepted Answer

chmod g+s dir. `chmod g+s dir` sets the setgid bit on a directory, causing new files created within it to inherit the directory's group ownership rather than the creator's primary group. This is a standard Linux permission mechanism for collaborative directories.

Answer

chmod u+s dir

Answer

chown developers: file

Answer

chmod g+s file

Question 10

A user wants to view the contents of a compressed file file.txt.gz without decompressing it permanently. Which two commands can be used? (Choose two.)

Accepted Answer

gunzip -c file.txt.gz. `gunzip -c` decompresses the file to standard output, allowing the user to view the contents without modifying the original compressed file. Option B is correct because `zcat` is equivalent to `gunzip -c` and reads the compressed file directly, outputting the decompressed data to the terminal without permanent decompression.

Answer

gzip -l file.txt.gz

Answer

gzip -d file.txt.gz

Answer

gzip -k file.txt.gz

Question 11

Refer to the exhibit.

A user attempts to read /etc/passwd and receives "Permission denied". What is the most likely reason?

Accepted Answer

The user does not have execute permission on the /etc directory.. To read a file, a user needs both read permission on the file itself and execute permission on every directory in the path leading to it. The /etc directory typically has permissions 755 (drwxr-xr-x), which grants execute permission to the owner and group but not to others. If the user is not the owner and not in the group, they lack execute (x) on /etc, which prevents them from traversing into the directory to access /etc/passwd, even if the file's permissions would otherwise allow reading.

Answer

The user is not in the root group.

Answer

The file has the immutable attribute set.

Answer

The user does not have read permission on the file.

Question 12

Refer to the exhibit.

A user attempts to create a file in /backup/snapshots/ but receives an error. What is the most likely cause?

Accepted Answer

The /backup filesystem is mounted read-only.. The error occurs because the /backup filesystem is mounted read-only, which prevents any write operations, including file creation, regardless of directory permissions or available space. This is a common scenario when a filesystem is intentionally mounted with the 'ro' option in /etc/fstab or via the mount command to protect data integrity.

Answer

The /backup directory does not exist.

Answer

The user does not have write permission on /backup.

Answer

The /backup filesystem is full.

Question 13

Refer to the exhibit.

The /data directory needs to be resized to 15GB. What is the first step?

Accepted Answer

Unmount the filesystem.. The first step to resize a filesystem is to unmount it, because most filesystem resizing tools (such as resize2fs for ext4) require the filesystem to be unmounted to safely modify the underlying block device without risking data corruption. Attempting to resize a mounted filesystem can lead to inconsistent metadata and data loss. Unmounting ensures no processes are actively writing to the filesystem during the resize operation.

Answer

Resize the partition using fdisk.

Answer

Create a new partition and copy data.

Answer

Resize the filesystem using resize2fs.

Question 14

A system administrator needs to find all files in /var/log that have been modified in the last 7 days. Which command accomplishes this?

Accepted Answer

find /var/log -mtime -7. The `-mtime -7` option in the `find` command matches files whose content was modified less than 7 days ago (i.e., within the last 7 days). The minus sign before the number indicates 'less than' or 'within the last N days', which is exactly what the system administrator needs to find files modified in the last 7 days.

Answer

find /var/log -mtime +7

Answer

find /var/log -mtime 7

Answer

find /var/log -atime -7

Question 15

A user is unable to execute a script in their home directory. The script has permissions -rw-r--r--. Which command will allow the user to execute the script?

Accepted Answer

chmod u+x script.sh. The script's permissions -rw-r--r-- indicate the owner has read and write but not execute. Both `chmod u+x script.sh` (adds execute for owner) and `chmod 755 script.sh` (sets owner to rwx, group/others to r-x) grant the user execute permission, allowing them to run the script. Option B is the minimal change, but option D also works; thus both are correct. Options A and C are incorrect because they would either remove execute or only add it for 'others', not the user.

Answer

chmod a-x script.sh

Answer

chmod o+x script.sh